This project involves both clinical studies of humans infected with the intestinal nematode, Strongyloides stercoralis, and laboratory analysis of parasite antigens and immunologic responses to them. The parasite is of particular interest because of its unusual biologic properties (no parasitic male worm, free-living stage, etc.), and the fact that it can produce serious, even fatal, disease in certain immunosuppressive states. We continue to have problems in purification of the larval protease which would probably be the optimum diagnostic skin test antigen (immediate reaction). Western blotting with IgE and histamine-releasing activity are the two types of assays for allergenic activity, but there are probably multiple antigens present capable of these properties. The association of strongyloides infection in patients infected with HTLV-1 retrovirus continues to be investigated. Many of these patients have very low total serum IgE levels so their cytokine responses are being examined. The parasite-specific IgE assay (ELISA) appears to be sensitive and specific. Another group of patients with strongyloides infection has become available for study from our collaboration with University of Massachusetts in assessing prevalence of this infection in Cambodian refugees in Lowell, Massachusetts. This study also involves comparative efficacy of treatment with Ivermection vs. thiabendazole.